Information recording medium

ABSTRACT

An information recording medium having at least a read only area and a recording and reproducing area is composed of at least: a substrate; a recording layer formed on the substrate so as to record and reproduce information; and a light transmission layer having transparency formed on the recording layer. The information recording medium is further characterized in that a wobbling groove corresponding to the read only area and another wobbling groove corresponding to the recording and reproducing area is formed on the substrate without overlapping with each other, the recording and light transmitting layers are continuously adhered over at least two areas of the read only area and the recording and reproducing area, reflectivity of the recording layer is more than 5%, and a push-pull signal output T 3  reproduced from the read only area and another push-pull signal output T 4  reproduced from the recording and reproducing area before recording satisfies relations of T 3 ≧0.1, T 4 ≧0.1 and 1.5≧T 3 /T 4 ≧0.5.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an information recording mediumthat is used for an optical recording and reproducing apparatus, whichreads out information from the information recording medium with makingthe information recording medium move relatively, particularly, relatesto an information recording medium having a read only area from whichinformation can be read out together with a recording and reproducingarea in which information can be recorded and from which the informationcan be reproduced.

[0003] 2. Description of the Related Art

[0004] Until now, there is provided an information recording medium in ashape such as disciform, card and tape as a system of opticalinformation recording medium, which is used for reading out informationfrom the information recording medium that is made relatively move. On abasis of recording or reproducing mechanism, such an informationrecording medium is divided into two types; one is a read-only type andthe other is a recording and reproducing type (including recordable typeand over-writable type). In other words, the former-type recordingmedium is prerecorded with information and forwarded in a market, andthen a user just reproduces the information from the former-typerecording medium. The latter-type recording medium is forwarded in amarket without recording information. A user newly records informationin the latter-type recording medium, and then the user reproduces theinformation from the latter-type recording medium.

[0005] On the contrary, in accordance with advancing multimedia in theworld, it is increasing that a copyright is infringed by an electronicmethod and resulted in a remarkable problem. Consequently, it isrequired for even a recording and reproducing type information recordingmedium, which can be recorded by a user freely, to embed a specificcode, which can not be rewritten by a user, in an information recordingmedium so as to protect a copyright from such infringement.

[0006] From the point of view of such a copyright protection, there hasbeen provided various kinds of information recording mediums. Each ofthem has two areas together; one is a read only area that is recordedwith permanent data, which can not be rewritten, and the other is arecording and reproducing area that is recordable (or a recording andreproducing area that is rewritable repeatedly). It is popular that aninformation recording medium, for example, is constituted by a read onlyarea, which is composed of a pit array and prerecorded with a specificdata, and a recording and reproducing area, which is composed of acontinuous substance of grooves. A phase change type informationrecording medium such as a DVD-RAM (Digital Versatile Disc-Random AccessMemory) and a DVD-RW (Digital Versatile Disk-ReWritable) has been putinto practice. A user records information in a recording and reproducingarea of such an information recording medium as user recording.

[0007] Incidentally, it is studied that a method of recording apermanent data by using a wobbling groove in conjunction withconstituting a read only area by a groove instead of a pit array. If thepermanent data is recorded by a wobbling groove as mentioned above, theoriginal permanent data can be distinguished from altered permanentdata, which have been forged by a person of counterfeiting, and resultedin disclosing a fact of infringing a copyright easily because such aperson of counterfeiting can record the permanent data only through thephase-change recording method. In other words, he can record thepermanent data by the pit-array recording method, which uses differenceof reflectivity.

[0008] Accordingly, constituting a read only area by a groove canadvance copy protection more than by the conventional pit-arrayrecording method.

[0009] The inventor of the present invention has manufactured anabove-mentioned information recording medium actually as a trial andreproduced the information recording medium, and then he recorded theinformation recording medium with information and reproduced theinformation. Consequently, he found some problems related toreproduction.

[0010]FIG. 19 is a plan view of an information recording medium 90manufactured as a trial. The information recording medium 90 is composedof a read only area 93 and a recording and reproducing area 94. Further,both of the read only area 93 and the recording and reproducing area 94are constituted by a groove. The read only area 93 is recorded with aspecific code data for copy protection by a wobbling groove and therecording and reproducing area 94 is recorded with a location data,which is a reference data that is essential while recording, by awobbling groove. When recording the specific code data and the locationdata, a shape of groove is optimized. In the read only area 93, theshape of groove is optimized so as for an output of the specific codedata to be maximum. In the recording and reproducing area 94, userrecording is performed while reading the location data and the shape ofgroove is optimized so as for a reproduction error rate at the time tobe minimized.

[0011] The information recording medium 90 constituted as mentionedabove has been loaded in various kinds of recording and reproducingapparatuses and operated. However, some problems such that traversingtwo areas has hardly performed smoothly and tracking has been out ofcontrol happened. In other words, when trying to read a location data inthe recording and reproducing area 94 after reading out a specific codedata for copy protection from the read only area 93, tracking hasdeviated off the control frequently.

[0012] This is caused by that functions of respective areas aredifferent from each other. Further, characteristics of previouslyrecorded data are also different from each other. Consequently, it isfound that groove shapes of two areas are different from each other ifthe functions and characteristics are optimized in accordance withrespective purposes and continuous reproduction with traversing throughboth areas can not be conducted.

SUMMARY OF THE INVENTION

[0013] Accordingly, in consideration of the above-mentioned problems ofthe prior art, an object of the present invention is to provide aninformation recording medium, which solves a tracking problem ofdeviating off the control that happens when traversing two differentareas.

[0014] In order to achieve the above object, the present inventionprovides, according to an aspect thereof, an information recordingmedium, which has at least a read only area and a recording andreproducing area. The information recording are is composed of at least:a substrate; a recording layer formed on the substrate so as to recordand reproduce information; and a light transmission layer havingtransparency formed on the recording layer. The information recordingmedium is further characterized in that a wobbling groove correspondingto the read only area and another wobbling groove corresponding to therecording and reproducing area is formed on the substrate withoutoverlapping with each other, the recording and light transmitting layersare continuously adhered over at least two areas of the read only areaand the recording and reproducing area, reflectivity of the recordinglayer is more than 5%, and a push-pull signal output T3 reproduced fromthe read only area and another push-pull signal output T4 reproducedfrom the recording and reproducing area before recording satisfiesrelations of T3≧0.1, T4≧0.1 and 1.5≧T3/T4≧0.5.

[0015] Other object and further features of the present invention willbe apparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0016]FIG. 1 is a plan view of an information recording medium indisciform according to a first embodiment of the present invention.

[0017]FIG. 2 is a cross sectional view of the information recordingmedium shown in FIG. 1 exhibiting a most fundamental configuration.

[0018]FIG. 3 is an enlarged plan view of the information recordingmedium shown in FIG. 2 exhibiting a vicinity of boundary area between aread only area and a recording and reproducing area.

[0019]FIG. 4 is an enlarged plan view of an information recording mediumrecorded with a record mark showing a vicinity of boundary area betweena read only area and a recording and reproducing area according to thefirst embodiment of the present invention.

[0020]FIG. 5 is a plan view of a 4-division detector used for recordingand reproducing the information recording medium according to thepresent invention.

[0021]FIG. 6 is a table exhibiting relationship between a push-pulloutput T3 and tracking performance of the information recording mediumaccording to the first embodiment of the present invention.

[0022]FIG. 7 is a table exhibiting relationship between a push-pulloutput T4 and tracking performance of the information recording mediumaccording to the first embodiment of the present invention.

[0023]FIG. 8 is a table exhibiting relationship between a ratio ofpush-pull output T3 to T4 and tracking performance of the informationrecording medium according to the present invention.

[0024]FIG. 9 is a graph showing relationship between a groove depth in aread only area and a push-pull output T3 of the information recordingmedium according to the present invention.

[0025]FIG. 10 is a plan view of a read only area of the informationrecording medium according to the present invention.

[0026]FIG. 11 is a plan view of a recording and reproducing area of theinformation recording medium according to the present invention.

[0027]FIG. 12 is a waveform of digital date modulated by thefrequency-shift keying method.

[0028]FIG. 13 is a waveform of digital date modulated by the phase-shiftkeying method.

[0029]FIG. 14 is a waveform of digital date modulated by theamplitude-shift keying method.

[0030]FIG. 15 is a table exhibiting data change before and aftermodulating a base-band.

[0031]FIG. 16 is a table exhibiting an example of actual data changebefore and after modulating a base-band.

[0032]FIG. 17 is an information recording medium in a card shapeaccording to a second embodiment of the present invention.

[0033]FIG. 18 is another information recording medium in a card shapeaccording to the second embodiment of the present invention.

[0034]FIG. 19 is a plan view of an information recording medium indisciform according to the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] [First Embodiment]

[0036]FIG. 1 is an enlarged plan view of an information recording mediumin disciform according to a first embodiment of the present invention.In FIG. 1, an information recording medium 1 is composed of at least aread only area 30 and a recording and reproducing area 40, and providedwith a center hole “Q”. In the case of the information recording medium1 shown in FIG. 1, the read only area 30 and the recording andreproducing area 40 are disposed in the inner circumference side and theouter circumference side respectively. However, their disposition can beinverted. These two areas are formed not so as to overlap with eachother. In this case, these two areas are formed sequentially.

[0037] Further, in FIG. 1, the information recording medium 1 iscomposed of one read only area 30 and one recording and reproducing area40. However, the information recording medium 1 can be composed of aplurality of read only areas and a plurality of recording andreproducing areas.

[0038]FIG. 2 is a cross sectional view of the information recordingmedium 1 shown in FIG. 1 and shows a most fundamental configuration ofthe information recording medium 1 according to the first embodiment ofthe present invention. In FIG. 2, the information recording medium 1 iscomposed of at least a substrate 13, a recording layer 12 and a lighttransmitting layer 11. On the surface of the substrate 13, that is, aninterface between the substrate 13 and the recording layer 12,microscopic patterns corresponding to the read only area 30 and therecording and reproducing area 40 are formed without overlapping witheach other. As shown in FIG. 2, tracks TR31 and TR32 are formed as awobbling groove, which constitutes the read only area 30, and tracksTR41, TR42 and TR43 are formed as a wobbling groove, which constitutesthe recording and reproducing area 40. The grooves in these two areashave a depth of d3 for the read only area 30 and d4 for the recordingand reproducing area 40 respectively. It is acceptable that these twodepths are identical or different from each other. However, they must bein a certain depth, which can obtain a certain range of push-pull outputthat will be explained later. The substrate 13, the recording layer 12and the light transmitting layer 11 are formed in parallel with eachother. Further, the recording layer 12 and the light transmitting layer11 are continuously contacted with each other without being interrupted,wherein they cover whole areas of the read only area 30 and therecording and reproducing area 40.

[0039] The substrate 13 is a base, which has a function of supportingthe recording layer 12 and the light transmitting layer 11 formedthereon mechanically. With respect to a material for the substrate 13,any one of synthetic resin, ceramic and metal can be used. With respectto a typical example of the synthetic resin, there is provided variouskinds of thermoplastic resins and thermosetting resins such aspolycarbonate, polymethyle methacrylate, polystyrene, copolymer ofpolycarbonate and polystyrene, polyvinyl chloride, alicyclic polyolefinand polymethyle pentene, and various kinds of energy ray curable resinssuch as UV ray curable resins, visible radiation curable resins andelectron beam curable resins. They can be preferably used.

[0040] Further, it is also acceptable that these synthetic resins aremixed with metal powder or ceramic powder. With respect to a typicalexample of the ceramic, soda lime glass, soda aluminosilicate glass,borosilicate glass or silica glass can be used. With respect to atypical example of the metal, a metal plate such as aluminum that has notransparency can be used. A thickness of the substrate 13 is suitable tobe within a range of 0.3 mm to 3 mm, desirably 0.5 mm to 2 mm due tonecessity of supporting mechanically the information recording medium 1in total. In a case that the information recording medium 1 isdisciform, the thickness of the substrate 13 is desirable to be designedsuch that the total thickness of the information recording medium 1including the substrate 13, the recording layer 12 and the lighttransmitting layer 11 becomes 1.2 mm, for the purpose ofinterchangeability with a conventional optical disc. A printing forindicating contents of the information recording medium 1 or a trademarkcan be printed on the surface of the substrate 13 opposite to therecording layer 12, if necessary.

[0041] The recording layer 12 has a function of reading out information,recording information or rewriting information and is a thin film layerthat is constituted by a recording material having reflectivity of morethan 5% at a wavelength λ. With respect to a material for the recordinglayer 12, a material that is represented by a phase-change material ofwhich reflectivity or refractive index changes in a process of beforeand after recording, a magneto-optical material, which reproduces achange of Kerr rotation angle or a dye material of which refractiveindex or a depth changes in a process of before and after recording isused.

[0042] With respect to a typical example of the phase-change material,an alloy of element such as indium, antimony, tellurium, selenium,germanium, bismuth, vanadium, gallium, platinum, gold, silver, copper,aluminum, silicon, palladium, tin and arsenic can be used, wherein analloy includes a compound such as oxide, nitride, carbide, sulfide andfluoride. Particularly, an alloy such as Ge—Sb—Te system, Ag—In—Te—Sbsystem, Cu—Al—Sb—Te system and Ag—Al—Sb—Te system is suitably used.These alloys can contain one or more elements as a trace of additiveelement within a range of more than 0.01 atomic % and less than 10atomic % in total. Such an additive element is selected out of Cu, Ba,Co, Cr, Ni, Pt, Si, Sr, Au, Cd, Li, Mo, Mn, Zn, Fe, Pb, Na, Cs, Ga, Pd,Bi, Sn, Ti, V, Ge, Se, S, As, Tl, In and Ni. With respect tocompositions of each element, for example, there is existed Ge₂Sb₂Te₅,Ge₁Sb₂Te₄, Ge₈Sb₆₉Te₂₃, Ge₈Sb₇₄Te₁₈, Ge₅Sb₇₁Te₂₄, Ge₅Sb₇₆Te₁₉,Ge₁₀Sb₆₈Te₂₂ and Ge₁₀Sb₇₂Te₁₈ and a system adding a metal such as Sn andIn to the Ge—Sb—Te system as for the Ge—Sb—Te system.

[0043] Further, as for the Ag—In—Sb—Te system, there is existedAg₄In₄Sb₆₆Te₂₆, Ag₄In₄Sb₆₄Te₂₈, Ag₂In₆Sb₆₄Te₂₈, Ag₃In₅Sb₆₄Te₂₈,Ag₂In₆Sb₆₆Te₂₆, and a system adding a metal or semiconductor such as Cu,Fe and Ge to the Ag—In—Sb—Te system.

[0044] With respect to an actual example of the magneto-opticalmaterial, there is existed alloys composed of an element such asterbium, cobalt, iron, gadolinium, chromium, neodymium, dysprosium,bismuth, palladium, samarium, holmium, praseodymium, manganese,titanium, palladium, erbium, ytterbium, lutetium and tin, wherein analloy includes a compound such as oxide, nitride, carbide, sulfide andfluoride. Particularly, constituting an alloy of a transition metal,which is represented by TbFeCo, GdFeCo and DyFeCo, with rare earthelement is preferable.

[0045] Moreover, using an alternate lamination layer of cobalt andplatinum can constitute the recording layer 12.

[0046] With respect to a dye material, porphyrin dye, cyanine dye,phthalocyanine pigment, naphthalocyanine pigment, azo dye,naphthoquinone dye, fulgide dye, polymethine dye and acridine dye can beused.

[0047] An auxiliary material can be contained in or laminated on therecording layer 12 so as to increase recording or reproducing abilityother than a material for recording. For example, a dielectric materialsuch as ZnS, SiO, ZnSSiO, GeN, SiN, SiC, AlN, MgF, ZrO and InO can belaminated on the recording material. Consequently, a number ofrewritings and luminous energy for reproducing can be improved.

[0048] Further, in order to increase luminous energy for reproducingextremely, a light reflective film, that is, a heat sink made byaluminum, gold, silver or titanium can be laminated on the recordinglayer 12 together with a dielectric material.

[0049] Furthermore, in order to conduct high-density recording andreproducing, a well-known super-resolution film or so-called mask filmcan be laminated on the recording layer 12 together with the lightreflective film.

[0050] Optical recording or reproducing is conducted to the recordinglayer 12. A laser beam having a wavelength of λ nm, which is convergedby an objective lens having a numerical aperture NA, is transmittedthrough the light transmitting layer 11. In other words, the lighttransmitting layer 11 has a function of conducting the convergedreproducing light to the recording layer 12 with maintaining thereproducing light under a condition of lesser optical distortion. Amaterial having a light transmittance of more than 70%, for example,desirably more than 80% with respect to the reproducing light having thewavelength λ can be suitably used for the light transmitting layer 11.

[0051] Further, the light transmitting layer 11 has a predeterminedrefractive index “n” at the wavelength λ. It is desirable for the lighttransmitting layer 11 that the refractive index “n” is within a range of1.4 to 1.7 with respect to interchangeability with a conventionaloptical disc, more desirably, the refractive index “n” is within a rangeof 1.45 to 1.65.

[0052] Furthermore, if birefringence of a material is assigned to beless than 100 nm, desirably less than 50 nm, more desirably less than 35nm at double paths, a change of reproduction output can be suppressedsufficiently. Materials having such a characteristic such aspolycarbonate, polymethyle methacrylate, cellulose triacetate, cellulosediacetate, polystyrene, copolymer of polycarbonate and polystyrene,polyvinyl chloride, alicyclic polyolefin and polymethyle pentene can beused for the light transmitting layer 11.

[0053] Moreover, it can be acceptable for the light transmitting layer11 to have a function of protecting the recording layer 12 mechanicallyand chemically. With respect to materials having such a function, amaterial having higher stiffness like, for example, transparent ceramicssuch as soda lime glass, soda aluminosilicate glass, borosilicate glassand silica glass, thermosetting plastics, energy ray curable resins suchas UV ray curable resins, visible radiation curable resins and electronbeam curable resins, moisture curable resins and plural liquid mixturecurable resins can be suitably used for the light transmitting layer 11.With respect to a thickness of the light transmitting layer 11, it isdesired to be less than 2 mm, particularly, less than 1.2 mm so as toreduce birefringence or optical anisotropy.

[0054] In a case that an objective lens having a numerical aperture NAof more than 0.7 is installed in a reproducing apparatus for aninformation recording medium and used, a thickness of the lighttransmitting layer 11 is desired to be less than 0.4 mm from a point ofview that optical aberration can be suppressed when the informationrecording medium 1 is slanted with respect to a reproducing light beamor recording light beam. Particularly, in a case that the NA is morethan 0.85, the thickness is desirable to be less than 0.12 mm. Fromanother point of view of preventing the recording layer 12 from ascratch, it is desired to be more than 0.02 mm. In other words, thethickness is desired to be within a range of 0.02 mm to 0.12 mm if theNA is more than 0.85.

[0055] Further, scattering of thickness in one plane shall be ±0.003 mmat the maximum, desirably less than ±0.002 mm, more desirably less than±0.001 mm.

[0056] Furthermore, it is acceptable for the light transmitting layer 11to be constituted by not only a single layer as shown in FIG. 2 but alsolamination of a plurality of layers having similar functions.

[0057] More, a commonly known antistatic layer can be formed on thesurface of the light transmitting layer 11 opposite to the recordinglayer 12 so as to reduce dust that attaches to the surface of the lighttransmitting layer 11.

[0058] Moreover, for a purpose of reducing affection of accidentalcollision with the light transmitting layer 11 caused by an objectivelens that constitutes a pickup of a reproducing apparatus or a recordingapparatus, a hard coat layer and a lubricative layer can be formed onthe light transmitting layer 11 on the opposite side to the recordinglayer 12 although the hard coat and lubricative layers are not shown indrawings.

[0059] With respect to an actual material for the hard coat layer, aresin, which transmits more than 70% of light having wavelength λ, suchas thermosetting resins, various energy ray curable resins (including UVray curable resins, visible radiation curable resins and electron beamcurable resins), moisture curable resin, plural liquid mixture curableresin and thermoplastic resin containing solvent can be used.

[0060] The hard coat layer mentioned above is desirable to exceed acertain value of the “scratch test by pencil” regulated by the JapaneseIndustrial Standard (JIS) K5400 in consideration of abrasion resistanceof the light transmitting layer 11. In consideration of that a hardestmaterial of the objective lens is glass, a value of the “scratch test bypencil” for the hard coat layer is most preferable to be more than the“H” grade. If the test value is less than the “H” grade, dust that iscaused by scraping the hard coat layer is remarkably generated.Consequently, an error rate is deteriorated abruptly. Thickness of thehard coat layer is desirable to be more than 0.001 mm in considerationof shock resistance, more desirable to be less than 0.01 mm inconsideration of warp of an total information recording medium 1.

[0061] With respect to other materials for the hard coat layer, anelement, which transmits more than 70% of light having a wavelength λand has a value of the “scratch test by pencil” of more than the “H”grade, such as carbon, molybdenum and silicon, and their alloy thatincludes composition such as oxide, nitride, sulfide, fluoride andcarbide can be used, wherein its film thickness is within a range of 1nm to 1000 nm.

[0062] With respect to an actual material for the lubricative layer,liquid lubricant of which surface energy is adjusted by modifyinghydrocarbon macromolecule with silicon and fluorine can be used.Thickness of the lubricative layer is desirable to be within a range of0.1 nm to 10 nm approximately.

[0063] A label printing can be applied on the surface of the substrate13 on the opposite side to the recording layer 12 although the labelprinting is not shown in any drawings. Various energy ray curable resinscontaining pigment and dye such as UV ray curable resins, visibleradiation curable resins and electron beam curable resins can be usedsuitably for the label printing. Thickness of the label printing isdesirable to be more than 0.001 mm in consideration of visibility of theprinting, more desirable to be less than 0.05 mm in consideration ofwarp of the total information recording medium 11. With respect to aprinting method, a screen printing method and an offset printing methodcan be used.

[0064] An information recording medium 1 can be installed in a cartridgeso as to improve ability of loading the information recording medium 1into a reproducing apparatus and improve protectiveness of theinformation recording medium 1 while loading and unloading.

[0065] A data that is recorded in an information recording medium 1according to the present invention as a permanent data in a wobblinggroove and its recording method is explained next.

[0066] In a read only area 30 of an information recording medium 1according to the present invention, a control data is embedded so as toinitiate reading out when loading the information recording medium 1into a player or initiating user recording into a recording andreproducing area 40. In other words, the control data is a specific codedata that is at least selected out from copyright related information, akey for encrypting, a key for deciphering, encrypted data, recordingpermission code, recording refusal code, reproduction permission code,reproduction refusal code, serial number, lot number, control number,manufacturer information, classification of the information recordingmedium, size of the information recording medium, ideal recording lineardensity of the information recording medium, ideal linear velocity ofthe information recording medium, track pitch of the informationrecording medium (at least one of P3 and P4 that will be depictedlater), recording strategy information, reproduction power informationand commonly known lead-in data. The specific code data is such a data,which is described by the decimal number system or the hexadecimalnotation and converted into the binary number system that includes a BCD(Binary-Coded Decimal) code and a gray code.

[0067] Further, the specific code data is recorded geometrically in theread only area 30 by wobbling a groove through any one modulation methodof the frequency-shift keying, phase-shift keying and amplitude-shiftkeying methods. A wobbling groove can be formed in any one shape ofline, coaxial and spiral. Particularly, in a case that a wobbling grooveconstituting the read only area 30 is in a spiral shape, the controldata can be recorded by either the CAV (Constant Angular Velocity)method or the CLV (Constant Linear Velocity) method.

[0068] Furthermore, the ZCAV (Zone Constant Angular Velocity) method orthe ZCLV (Zone Constant Linear Velocity) method can also be adopted byforming zones that vary by radius, wherein velocity control varies byeach zone. Data is recorded in a wobbling shape of groove and notrecorded by a pit array, so that the data can not be modifiedpermanently.

[0069] Moreover, the control data can contain a location data or a clockinformation, and further can contain an error correction code so as toreduce an error of reading out data.

[0070] According to the present invention, a location data, whichconducts readout all the time when a user recording in the recording andreproducing area 40 is initiated, are embedded in the recording andreproducing area 40 of the information recording medium 1. The locationdata is one of a data that is at least selected out from an absoluteaddress that is allocated to the whole area of the recording andreproducing area 40, a relative address that is allocated to a partialarea, a track number, a sector number, a frame number, a field number,time information and an error correction code. The location data is sucha data that is described by, for example, the decimal number system orthe hexadecimal notation and converted into the binary number systemthat includes a BCD code and a gray code.

[0071] Further, the location data is recorded geometrically in therecording and reproducing area 40 by wobbling a groove through any onemodulation method of the frequency-shift keying, phase-shift keying andamplitude-shift keying methods.

[0072] Furthermore, in a case that a location data is also recorded inthe read only area 30, it is acceptable to the location data that thelocation data is continuous or discontinuous with a location data to berecorded in the recording and reproducing area 40.

[0073] More, a part of contents of control data that is recorded in theread only area 30 can be recorded in the recording and reproducing area40 in addition to a location data to be recorded in the recording andreproducing area 40.

[0074] A wobbling groove can be formed in any one shape of line, coaxialand spiral. Particularly, in a case that a wobbling groove constitutingthe read only area 30 is in a spiral shape, the control data can berecorded by either the CAV method or the CLV method.

[0075] Further, the ZCAV method or the ZCLV method can also be adoptedby forming zones that vary by radius, wherein velocity control varies byeach zone.

[0076] With respect to the modulation methods of frequency-shift keying,phase-shift keying and amplitude-shift keying, they will be detailedlater.

[0077] The information recording medium 1 is complemented with respectto a plane structure hereinafter.

[0078] A plane structure of the information recording medium 1 is atleast composed of the read only area 30 and the recording andreproducing area 40 as shown in FIG. 1. These areas have a planestructure shown in FIG. 3.

[0079]FIG. 3 is an enlarged plan view of the information recordingmedium 1 shown in FIG. 2 exhibiting a vicinity of boundary area betweenthe read only area 30 and the recording and reproducing area 40. In FIG.3, tracks Tr31 and Tr32, which are a part of tracks constituting theread only area 30, and tracks Tr41, Tr42 and Tr43, which are a part oftracks constituting the recording and reproducing area 40, are exhibitedrepresentatively. A plurality of tracks that constitute the read onlyarea 30 is a groove and a control data is recorded by a wobbling groovealthough the wobbling groove is not illustrated in FIG. 3. A track pitchbetween center axes of each track is P3, wherein the track pitch P3 isillustrated in FIG. 3 as a distance between the tracks Tr31 and Tr32.

[0080] Further, a plurality of tracks that constitute the recording andreproducing area 40 is a groove and a location data is recorded thereinby a wobbling groove. However the wobbling is not illustrated in FIG. 3.A track pitch between center axes of each track is P4, wherein the trackpitch P4 is illustrated in FIG. 3 as a distance between the tracks Tr41and Tr42.

[0081] Values of these track pitches P3 and P4 are P3≦λ/NA and P4≦λ/NArespectively. It is acceptable to the track pitches P3 and P4 that theyare an identical value to or different values from each other. In a caseof using a violaceous laser beam and a pickup having high NA, forexample, the track pitches P3 and P4 are configured by P3≦476 nm andP4≦476 nm respectively with assigning that λ=405 nm and NA=0.85.

[0082] A space between the read only area 30 and the recording andreproducing area 40, that is, a distance between the track Tr32 and thetrack Tr41 shown in FIG. 3 is less than 25 μm as a minimal essentialcondition so as to obtain continuity of tracking.

[0083] Further, a desirable space between the read only area 30 and therecording and reproducing area 40, that is, the distance between thetracks Tr32 and Tr41 shall be the same value as either P3 or P4. In acase that P3 and P4 is extremely different from each other, it isdesirable for the distance to be assigned as an arbitrary value betweenP3 and P4, particularly, it is more desirable for the distance to beassigned as an average value of P3 and P4.

[0084] Most desirably, each of the space between the read only area 30and the recording and reproducing area 40, P3 and P4 is exactly the samevalue.

[0085] In the sense of minimizing impact when traversing areas, it isacceptable to provide a transition area that is composed of a groove ofmore than one track between the read only area 30 and the recording andreproducing area 40.

[0086] Further, in the transition area, it is acceptable to a trackpitch that the track pitch changes continuously or changes in multiplesteps from P3 to P4.

[0087] Furthermore, a groove that constitutes the transition area isessentially not recorded with data or not wobbled. However, it isacceptable to the groove that the groove is a wobbling groove, which isrecorded with a null data, that is, a data of “0” (zero) or a dummydata.

[0088] A wobbling groove amplitude of each area of the read only area 30and the recording and reproducing area 40 is formed with having arelationship such as less than a pitch that constitutes each area. Inother words, a wobbling groove amplitude of the read only area 30 isless than P3 and a wobbling groove amplitude of the recording andreproducing area 40 is less than P4.

[0089] A plane constitution of an information recording medium 2 isexplained next when a user initiates recording on the informationrecording medium 1.

[0090]FIG. 4 is an enlarged plan view of an information recording medium2 showing a vicinity of boundary area between a read only area 30 and arecording and reproducing area 40, wherein the information recordingmedium 2 exhibits a state after a user initiates recording on theinformation recording medium 1 shown in FIG. 3. In other words, the usermakes recording only in the recording and reproducing area 40 of theinformation recording medium 1. FIG. 4 representatively shows a statethat is recorded by a phase change recording method, particularly, by aso-called “high to low” method. In FIG. 4, a user data is recorded onlyon the tracks Tr41 and Tr42 in the recording and reproducing area 40 anda plurality of record marks M is recorded on the tracks Tr41 and Tr42.The “high to low” method means a method such that a recording layer 12is crystals and high in reflectivity when not recorded while therecording layer 12 is amorphous and low in reflectivity when recorded.As mentioned above, the user data is recorded by forming a record mark Mintermittently on a part of or all of the recording and reproducing area40 out of the read only area 30 and the recording and reproducing area40. Consequently, the information recording medium 2 is completed.

[0091] A signal method that is used for user data recording is explainednext. A modulation signal of so-called a (d, k) code, for example, canbe used for the user data recording. Either a fixed length code or avariable length code can be applied for a (d, k) modulation signal.

[0092] With respect to an example of a (d, k) modulation in a fixedlength code, there is provided the EFM (Eight to Fourteen Modulation)method, the EFM plus (8-16 modulation) method and the (D8-15 modulation)method that is disclosed in the Japanese Patent Application Laid-openPublication No. 2000-286709, wherein it is defined that d=2 and k=10respectively.

[0093] Further, in a case that d=1 and k=9 respectively, there isprovided the (D4, 6 modulation) method that is disclosed in the JapanesePatent Application No. 2001-080205 (filed by the applicant, VictorCompany of Japan, Ltd.).

[0094] Furthermore, in a case that d=1 and k=7 respectively, there isprovided the (D1, 7 modulation) method that is disclosed in the JapanesePatent Application Laid-open Publication No. 2000-332613.

[0095] With respect to an example of a (d, k) modulation in a variablelength code, there is provided the (17PP modulation) method that isdisclosed in the Japanese Patent Application Laid-open Publication No.11-346154/1999, wherein it is defined that d=1 and k=7 respectively.

[0096] A push-pull output, which is a major point of the informationrecording medium 1 according to the present invention, is explainednext. The information recording medium 1 of the present invention iscomposed of at least the read only area 30 and the recording andreproducing area 40 as mentioned above. A groove shape of each area canbe optimized in accordance with their purposes. In other words, a grooveshape is optimized so as to increase an output of control data in theread only area 30. In the recording and reproducing area 40, a grooveshape is optimized so as to initiate user recording together withreading a location data and so as to minimized a reproduction error rateat the moment. At this moment, a push-pull signal output T3 that isreproduced from the read only area 30 and another push-pull signaloutput T4 that is reproduced from the recording and reproducing area 40shall be defined so as to satisfy equations such as T3≧0.1 and T4≧0.1,and further so as to satisfy a relationship between T3 and T4 such as1.5≧T3/T4≧0.5. A push-pull output hereupon is a differential signal ineach area when traversing a groove.

[0097]FIG. 5 is a diagrammatic plan view of a 4-division detector 10that is used in a pickup of a recording and reproducing apparatus for aninformation recording medium in disciform. With referring to FIG. 5, amethod of measuring a push-pull output is explained. In FIG. 5, avertical line or the Y-axis is a radial direction of an informationrecording medium in disciform, that is, a direction of traversing agroove and a horizontal line or the X-axis is a tangential direction ora track direction of the information recording medium. The relationbetween vertical and horizontal directions corresponds to that of theinformation recording medium 1 shown in FIG. 3 if the informationrecording medium 1 is in disciform.

[0098] In FIG. 5, reproduction outputs of the 4-division detector 10 areIa, Ib, Ic and Id respectively. A difference between the innercircumference side and the outer circumference side, that is,|(Ia+Ib)−(Ic+Id)| is measured by the AC (Alternating Current) couplingmethod, and then a total sum, that is |(Ia+Ib+Ic+Id)51 is measured bythe DC (Direct Current) coupling method. A push-pull output T is a ratioof the difference to the total sum. The push-pull output T is defined asT=|(Ia+Ib)−(Ic+Id)|/|(Ia+Ib+Ic+Id)|. By this definition, a push-pulloutput T3 of the read only area 30 and a push-pull output T4 of therecording and reproducing area 40 is measured respectively.

[0099] In order to enable an area traversing reproduction across theread only area 30 and the recording and reproducing area 40, theinventor of the present invention produces an information recordingmedium 1 in disciform in which those push-pull outputs can be obtainedby adjusting depths d3 and d4 of each area and examines actualtraversing performance, and then a suitable range of push-pull output isobtained. The result of examination is exhibited in FIGS. 6, 7 and 8.

[0100]FIG. 6 is a table exhibiting the result of examination instability of tracking in the read only area 30 when a push-pull outputT3 of the read only area 30 is changed. The examination is performed inthe surrounding of a clean room and under a condition of a disceccentricity that is sufficiently restricted. As shown in FIG. 6,tracking is completely impossible when the push-pull output T3 is lessthan 0.08.

[0101]FIG. 7 is a table exhibiting the result of examination instability of tracking in the recording and reproducing area 40 when apush-pull output T4 of the recording and reproducing area 40 is changed.The examination is performed in the surrounding of a clean room andunder a condition of a disc eccentricity that is sufficientlyrestricted. As shown in FIG. 7, tracking is completely impossible whenthe push-pull output T4 is less than 0.08 as same as the result of theread only area 30.

[0102]FIG. 8 is a table exhibiting the result of examination instability of tracking during 2-area traversing reproduction when thepush-pull output T3 of the read only area 30 is changed together withthe push-pull output T4 of the recording and reproducing area 40. Theexamination is performed under a condition of a disc eccentricity thatis sufficiently restricted. As shown in FIG. 8, it is apparent that the2-area traversing reproduction is possible only within a range of1.5≧T3/T4≧0.5. A reason why the push-pull output ratio of two areas mustbe less than a predetermined value is that servo will not follow ifdifference of push-pull outputs is excessively large and resulted in outof tracking. In other words, it is caused by that there is a limit in adynamic range of player servo circuit.

[0103] In summarizing the result of examinations mentioned above, acondition of enabling the 2-area traversing reproduction is as follows:

T3≧0.1,

T4≧0.1 and

1.5≧T3/T4≧0.5.

[0104] The above relations are essential to be satisfied simultaneously.

[0105] The above-mentioned examinations are conducted under an idealcondition such that eccentricity of the information recording medium 1in disciform is sufficiently restricted. However, a center hole of anactual mass-produced disc is not uniform in accuracy. In considerationof that eccentricity of the information recording medium 1 in disciformis approximately within a range of 40 μm to 70 μm according to thecurrent technology, a desirable range of stabilizing the area traversingreproduction more is as follows:

T3≧0.15,

T4≧0.15 and

1.45≧T3/T4≧0.6.

[0106] The above relations are essential to be satisfied simultaneously.

[0107] Further, the above-mentioned examinations are conducted under thesurrounding of a clean room. However, actually mass-produced disc andplayer are handled in the general atmosphere. In consideration of thatan information recording medium 1 is attached with dust, a desirablerange of stabilizing the area traversing reproduction furthermore is asfollows:

T3≧0.20,

T4≧0.20 and

1.4≧T3/T4≧0.7.

[0108] The above relations are essential to be satisfied simultaneously.

[0109] Furthermore, the push-pull outputs T3 and T4 are defined by thetrack pitches P3 and P4, groove widths of the read only area 30 and therecording and reproducing area 40 and the groove depths d3 and d4respectively.

[0110]FIG. 9 is a graph showing relationship between a groove depth anda push-pull output T3 in the read only area 30 with defining that λ is405 nm, NA is 0.85, a refractive index “n” is 1.6, P3 is 0.32 μm and agroove width is 0.16 μm. The graph is shown by changing only the groovedepth d3. Parameters nd3/λ and T3 are allocated on the X-axis and theY-axis respectively. In FIG. 9, T3 is maximum at the point ofnd3/λ=0.125 and T3 is within a range of 0 to 0.45. With respect to apush-pull output T4 in the recording and recording area 40, a trend ofgraph is identical to that of T3.

[0111] Accordingly, under the above mentioned parameters, a mostsuitable range for T3 and T4 is as follows:

0.45≧T3≧0.20,

0.45≧T4≧0.20 and

1.4≧T3/T4≧0.7.

[0112] Further, in view of the relationship between the push-pull outputand the groove depth shown in FIG. 9, it should be understood that themost suitable range mentioned above can be realized by changing eachgroove depth of d3 and d4 in the read only area 30 and the recording andreproducing area 40 respectively.

[0113] Furthermore, it should also be understood that the most suitablerange can be realized by changing each track pitch of P3 and P4 in theread only area 30 and the recording and reproducing area 40respectively. If the track pitch P3 is assigned to be a relatively largevalue, for example, a value of the push-pull output T3 can be increased,wherein their relations can be arranged reversely. The push-pull outputcan be optimized by making use of characteristics of a data to berecorded in the read only area 30 and the recording and reproducing area40.

[0114]FIG. 10 shows wobbling grooves of tracks Tr31 and Tr32 in a readonly area 30. In FIG. 10, a control data 300 is recorded in the readonly area 30 in a shape of wobbling groove. As mentioned above, thecontrol data 300 is read out when an information recording medium 1 isloaded or a user recording is initiated. Although a recording capacityof the control data 300 itself is relatively low, a same data isrecorded 100 times to 1000 times repeatedly so as to be read in rapidly.Consequently, the control data 300 is written in a track as long as atleast more than one circle in the information recording medium 1. Insuch a read only area 30, a data in the track Tr31 interferes withanother data in the track Tr32, that is, the data in the track Tr31makes crosstalk to the other data in the track Tr32, so that it isdesirable for the track pitch P3 to be assigned in a larger value. Inother words, the track pitch P3 can be assigned to be larger than thetrack pitch P4 as far as the above-mentioned range is satisfied.Therefore, by assigning that d4=d3=22 nm, P4=320 nm and P3=350 nm, forexample, a control data 300 that is less in crosstalk can be obtainedwith maintaining stability of continuous reproduction. In order toincrease an output when reproducing, the groove depth d3 can be assignedto be larger than the groove depth d4. In other words, by assigning thatP4=320 nm, P3=350 nm, d4=22 nm and d3=28 nm, for example, a control data300 that is less in crosstalk can be obtained with maintaining stabilityof continuous reproduction.

[0115]FIG. 11 shows wobbling grooves of tracks Tr41 and Tr42 in arecording and reproducing area 40. In FIG. 11, a location data 400 and aclock data 450 is recorded in the recording and reproducing area 40 in ashape of wobbling groove. As mentioned above, the location data 400 isread out when a user recording is initiated and during a recording. Arecording capacity of the location data 400 itself is relatively low.

[0116] Further, it is essential that an accurate reference clock isproduced during a recording, so that the clock data 450 is allocated ina gap of the location data 400. The clock data 450 is a sinusoidal wavein a single frequency, for example, and a length of the clock data 450is more than 10 times longer than that of the location data 400.Consequently, as shown in FIG. 11, the location data 400 is extremelylow in a probability of overlapping with other location data 400 in anadjacent track, so that a data hardly interferes with others or hardlymakes crosstalk to others. In other words, the track pitch P4 can beassigned to be relatively small and resulted in realizing an informationrecording medium 1 in high density.

[0117] With respect to a groove depth d4, the groove depth d4 can beassigned to be relatively large so as to increase outputs of thelocation data 400 and the clock data 450 when reproducing. However, inview of a user recording, a shallower groove depth d4 can increase amodulation factor and decrease an error rate. Therefore, a relativelysmall figure is suitable for the groove depth d4.

[0118] Several points to be considered when designing the informationrecording medium 1 are explained above. However, it should be understoodthat the track pitches P3 and P4, the groove depths d3 and d4 and groovewidths of the read only area 30 and the recording and reproducing area40 are determined by considering parameters such as crosstalk andreproduction output of a control data 300, crosstalk and reproductionoutputs of a location data 400 and a clock data 450 and error rate of auser data totally. In this case, if the push-pull outputs T3 and T4 arewithin a predetermined range according to the present invention, atraversing across two areas can be performed smoothly.

[0119] In such an information recording medium 1 having the abovementioned configuration, a track such as Tr31 and Tr32, for example, isarranged on either one of so-called a groove G and a land L. The grooveG is a name of representing a groove that is close to a surface, whichis irradiated with an incident light beam, and the land L is a name ofrepresenting another groove that is far from the surface according tothe Japanese Industrial Standard JIS-X6271-1991, for example. It isstudied which of a groove G and a land L is more suitable for a track tobe arranged. The subject is closely related to another subject which ofa groove G and a land L is more suitable for a user to record on andreproduce from a recording layer 12 as well as for a recording of acontrol data and a location data. After studying from such a viewpoint,it is found that recording in a groove G selectively a user recordinginto the recording layer 12 can reduce reproduction jitter and a errorrate to a lower figure, and further exhibit an excellent repetitionperformance of recording. It is caused by that the groove G is closer toa laser beam than the land L, so that heat generated by irradiation ofthe laser beam accumulates in the groove G more than the land L. As aresult, recording sensitivity in the groove G becomes higher. Further, ashape of record mark that is formed in the groove G becomes uniform.Consequently, resulted in that an ideal recording can be realized in thegroove G.

[0120] On the other hand, in a case of recording such a record mark in aland L, heat generated by irradiation of the laser beam can releaseeasier than in a groove G, so that a record mark formed in the land Lbecomes uneven. Consequently, an ideal recording can not be realized inthe land L.

[0121] Accordingly, as shown in FIG. 2, a track such as Tr31 and Tr32 inthe read only area 30 is desirable to be allocated in a side that isclose to the light transmitting layer 11.

[0122] In addition thereto, the tracks Tr31 and Tr32 in the read onlyarea 30 are desirable to be allocated in a groove G that is close to thelight transmitting layer 11 from the viewpoint of continuity ofreproduction over to the recording and reproducing area 40.

[0123] A recording method of a control data and a location data to berecorded in an information recording medium 1 of the present inventionis explained next.

[0124] As mentioned above, a data such as a control data 300 and alocation data 400 are recorded geometrically by a wobbling groove in theread only area 30 and the recording and reproducing area 40 by using anyone method of the frequency-shift keying method, the phase-shift keyingmethod and the amplitude-shift keying method. It is acceptable thatmodulation methods for the control data 300 and the location data 400can be different from each other. However, the same modulation method isdesirable.

[0125] Further, a data can be either a binary data or a multi-valueddata. Hereinafter with defining that a data is a binary data, themethods of the frequency-shift keying method, the phase-shift keyingmethod and the amplitude-shift keying method are explained.

[0126] With respect to an actual recording by the frequency-shift keyingmethod, a data is recorded geometrically by using a high frequencysection and a low frequency section as shown in FIG. 12, for example.

[0127]FIG. 12 is a waveform of digital date (10110) that is recordedgeometrically by the frequency-shift keying method. In FIG. 12, acontrol data 300 or a location data 400 is composed of a plurality ofhigh frequency sections 501 a and 501 b (hereinafter genericallyreferred to as high frequency section 501) and a plurality of lowfrequency sections 500. The high frequency section 501 and the lowfrequency section 500 corresponds to the data bit “1” and the other databit “0” respectively. A frequency of a data bit is changed over at everyone channel bit in response to an original digital data and every databits are recorded in digital. A number of waves that constitute eachfrequency section is not limited to a specific number and one wave isconstituted by more than one cycle. However, in order to detect afrequency accurately in a reproducing apparatus and to obtain a certaindegree of transfer rate, each frequency section that corresponds to eachdata bit is desirably constituted by a number of waves within a range ofone cycle to 1000 cycles, more desirably one cycle to 30 cycles inconsideration of not being too redundant.

[0128] Further, each amplitude of the high frequency section 501 and thelow frequency section 500 can be the same as each other. However, anamplitude ratio is not limited to a specific figure, an amplitude of thehigh frequency section 501 can be formed larger than that of the lowfrequency section 500 in consideration of a frequency response of areproducing apparatus.

[0129] Furthermore, a physical length and an amplitude of a channel bit,which constitute the high frequency section 501 and the low frequencysection 500, is not limited to a specific figure.

[0130] As shown in FIG. 12, each amplitude of the high frequency section501 and the low frequency section 500 is identical to each other and thelength or the period of the high frequency section 501 can be identicalto that of the low frequency section 500. If the amplitude and theperiod is assigned as mentioned above, judging “0” or “1” whilereproducing can be performed by a sufficient amplitude threshold value.

[0131] Further, a serial data can be read out by one time thresholdvalue, so that a reproducing circuit can be simplified.

[0132] Furthermore, in a case that a jitter or fluctuation in the timeaxis direction is existed in a reproduced data, there is a merit of thatsuch an identical amplitude and period can minimize affection by thejitter.

[0133] Moreover, if a code to be recorded is ideally symmetric, a totallength of each period of the high frequency section 501 is equal to thatof the low frequency section 500, and resulted in that no direct currentcomponent exists in a reproduced signal. In other words, decoding thedata and servo controlling is released from excessive load, so that theideally symmetrical code is advantageous for data processing and servocontrolling.

[0134] A phase at a point of changing a channel bit from the highfrequency section 501 to the low frequency section 500 or vise versa canbe designated arbitrary. However, the high frequency section 501 and thelow frequency section 500 can be arranged so as to prevent a phase jumpand to maintain phase continuity at a channel bit changing-over point asshown in FIG. 12. In other words, a starting phase of the low frequencysection 500 is selected so as to be a same phase direction at a point ofconnecting an end of the high frequency section 501 with a beginning ofthe low frequency section 500.

[0135] Further, the reverse relationship between the high frequencysection 501 and the low frequency section 500 is the same situation, astarting phase of the high frequency section 501 is selected so as to bethe same phase direction at a point of connecting an end of the lowfrequency section 500 with a beginning of the high frequency section501. If a starting phase is selected as mentioned above, continuity ofphase is maintained and power efficiency is improved. In additionthereto, a reproduction envelope becomes constant, so that a data errorrate of an information recording medium 1 is improved.

[0136] Although selecting each frequency of the high frequency section501 and the low frequency section 500 is optional, a frequency of thehigh frequency section 501 is required not to be extremely higherfrequency than that of the lower frequency section 500 so as toeliminate interference with a frequency band that is used for recordinga data by a user.

[0137] On the other hand, in order to improve a reproduction error rateof an address data, it is desired for each frequency of the highfrequency section 501 and the low frequency section 500 that there isexisted a certain degree of frequency difference between them andseparation between them is kept excellently.

[0138] From the point of view mentioned above, it is desirable for afrequency ratio of the high frequency section 501 to the low frequencysection 500, that is, a frequency ratio of high frequency to lowfrequency to be within a range of 1.09 to 5.0. In other words, a phasedifference between two frequencies is desirable to be within a range of±π/12 to ±π/0.75, that is, 360±15 degrees to 360±240 degrees. Moredesirable to be within a range of 360±16 degrees to 360±210 degrees andmost desirable to be within a range of 360±16.5 degrees to 360±180degrees.

[0139] In the above-mentioned phase difference range, particularly, in acase that a frequency ratio of high frequency to low frequency isdefined to be 1.5 as shown in FIG. 12, two frequencies have a relationof shifting a phase of single frequency wave to −π/2.5 and +π/2.5respectively. In other words, they have a relation of shifting a phaseto 360±72 degrees. These frequencies can be expressed in that they areintegral multiple of a single frequency, wherein the integral multipleis three times and twice, and the single frequency is 0.5. Consequently,it is advantageous for a demodulation circuit to be simplified.

[0140] Further, producing a clock signal becomes easier by a circuithaving a window of 0.5.

[0141] Furthermore, a synchronous detection circuit can conductdemodulation. In this case, an error rate can be extremely reduced.

[0142] Actual recording processed by the phase-shift keying method isdetailed next.

[0143]FIG. 13 is a waveform of a digital date (10110) that is recordedgeometrically by the phase-shift keying method. In FIG. 13, a controldata 300 or a location data 400 is composed of a plurality of advancingphase sections 511 and a plurality of retreating phase sections 510. Theadvancing phase section 511 and the retreating phase section 510corresponds to the data bit “1” and the other data bit “0” respectively.A phase of each data bit is changed over at every one channel bit inresponse to an original digital data and every data bits are recorded indigital.

[0144] More accurately, the advancing phase section 511 is exhibited bythe sinusoidal wave of “sin 0” and the retreating phase section 510 isexhibited by the sinusoidal wave of “sin (−π)”. Each waveform of theadvancing phase section 511 and the retreating phase section 510 shownin FIG. 13 is constituted by one cycle of the sinusoidal wave. However,phase difference between them is as many as π, so that they can besufficiently separated and reproduced by the envelope detection methodor the synchronous detection method.

[0145] As shown in FIG. 13, frequencies of the advancing phase section511 and the retreating phase section 510 are the same as each other. Anumber of waves that constitute respective phase sections is not limitedto a specific number and one wave is constituted by more than one cycle.However, in order to detect a phase accurately in a reproducingapparatus and to obtain a certain degree of data transfer rate, eachphase section that corresponds to each data bit is desirably constitutedby a number of waves within a range of one cycle to 1000 cycles, moredesirably one cycle to 30 cycles in consideration of not being tooredundant.

[0146] Each physical length of the advancing phase section 511 and theretreating phase section 510 can be either the same as or different fromeach other. With defining that each physical length is the same as eachother, each one of serial data can be divided by a predetermined periodof time or clock, so that a reproducing circuit can be simplified.

[0147] Further, in a case that a jitter or fluctuation in the time axisdirection is existed in a reproduced data, there is a merit of that suchan identical physical length can minimize affection by the jitter.

[0148] Furthermore, a digital data recorded geometrically by thephase-shift keying method can be reproduced by the commonly knownsynchronous detection circuit in a low error rate.

[0149] It is acceptable that each amplitude of the advancing phasesection 511 and the retreating phase section 510 is either identical toor different from each other. However, it is desirable to be identicalto each other in consideration of ease of reproduction.

[0150] With respect to a phase difference between the advancing phasesection 511 and the retreating phase section 510, a limit of separationof the phase difference is obtained experimentally by applying toindividual information recording mediums 1. It is confirmed that a phasedifference can be separated up to π/8. In other words, a minimum phasedifference can be set to within a range of π/8 to π, wherein πcorresponds to a minimum phase difference of a binary data. In a case ofmulti-valued recording, a data from binary to hexadecimal value can betreated.

[0151] A single frequency to be a reference clock can be recorded bysuperimposing upon a control data 300 or a location data 400. In otherwords, a single frequency of which frequency is integral multiples(including one) of a fundamental frequency constituting respective phasesections or the fundamental frequency divided by a divisor of integralmultiple can be superimposed upon the control data 300 or the locationdata 400 that is recorded by the phase-shift keying method. In the caseof superimposing a clock frequency as mentioned above, separatingfrequencies can be realized by a commonly known band-pass filter.However, frequency difference between the fundamental frequency of thephase-shift keying method and the clock frequency is desired to belarge. In a case that a fundamental frequency of the phase-shift keyingmethod and a clock frequency is assigned to be “1” and “½” respectively,these frequencies are suitably separated and resulted in enabling toextract both data and clock stably.

[0152] Although it is not shown in any drawings, by using a saw-toothwaveform as a fundamental waveform, phase difference can be expressed bycontrolling each of rising edge and falling edge of the saw-toothwaveform independently. For example, it is acceptable that the data “1”and “0” are recorded geometrically with defining that the data “1” is asection having a gradually rising edge and a rapidly falling edge andthe other data “0” is another section having a rapidly rising edge and agradually falling edge. Such a data recording method by angulardifference between a rising edge and a falling edge can demodulate anoriginal data by extracting a differential component after inputtinginto a high-pass filter. Consequently, it is advantageous that theoriginal data can be reproduced by a simplified circuit configurationeven in a low C/N (Carrier to Noise ratio) circumstance.

[0153] An actual recording method by the amplitude-shift keying methodis explained next.

[0154]FIG. 14 is a waveform of a digital date (10110) that is recordedgeometrically by the amplitude-shift keying method. In FIG. 14, acontrol data 300 or a location data 400 is composed of a plurality ofamplitude sections 521 in which a groove is wobbled by a predeterminedperiod of time and a plurality of non-amplitude sections 520 in which agroove is not wobbled. The amplitude section 521 and the non-amplitudesection 520 corresponds to the data bit “1” and the other data bit “0”respectively. As shown in FIG. 14, the amplitude section 521 isconstituted by 3 cycles of a fundamental waveform. A number of cycles isnot limited to a specific number. However, in a case that the number ofcycles is too many, a length of the non-amplitude section 520 becomeslonger necessarily. A fundamental wave, which produces a gate whenreproducing, is hardly detected as a result. Consequently, a range of 2cycles to 100 cycles, more desirably a range of 3 cycles to 30 cycles issuitable for the amplitude section 521.

[0155] Further, no restriction is given to each length of the amplitudesection 521 and the non-amplitude section 520 or a figure of amplitudeof the amplitude section 521. If each amplitude of the plurality ofamplitude sections 521 is identical to each other and the length of theamplitude section 521 is identical to that of the non-amplitude section520 as shown in FIG. 14, a judgement of “1” or “0” can be performed by asufficient amplitude threshold value and further a serial data can beread out by one time threshold value when reproducing. Consequently, areproducing circuit can be simplified.

[0156] Furthermore, in a case that a jitter or fluctuation in the timeaxis direction is existed in a reproduced data, there is a merit of thatsuch an identical amplitude and length can minimize affection by thejitter.

[0157] Moreover, if a code to be recorded is ideally symmetric, a totallength of the plurality of the amplitude sections 521 is equal to thatof the plurality of the non-amplitude section 520, and resulted in thatno direct current component exists in a reproduced signal. In otherwords, decoding the data and servo controlling is released fromexcessive load, so that the ideally symmetrical code is advantageous fordata processing and servo controlling.

[0158] As mentioned above, the information recording medium 1 accordingto the present invention is composed of at least the read only area 30and the recording and reproducing area 40.

[0159] Further, a push-pull signal output is defined to be within apredetermined range so as to enable to perform the 2-area traversingreproduction.

[0160] Furthermore, the above-mentioned explanations are simplifiedexplanations so as to exhibit fundamental items of the presentinvention. Therefore, it should be understood that the present inventionwould not be restricted to the information recording medium 1 shown inFIGS. 1 through 14. It will be apparent that many changes, modificationsand variations in the arrangement of equipment and devices and inmaterials can be made without departing from the invention conceptdisclosed herein.

[0161] For example, with defining that a fundamental waveform of awobbling groove is a sinusoidal waveform and a saw-tooth waveform insome cases, the first embodiment of the information recording medium 1are depicted above. However, the fundamental waveform is not limited tothe sinusoidal or saw-tooth waveform. Any shape of waveform such astriangular waveform, rectangular waveform and trapezoid waveform can beused for the fundamental waveform. However, these waveforms containharmonic components. Therefore, selecting a frequency, which does notoverlap with a recording frequency range that is initiated by a userwhen recording in the recording layer 12, is desirable when such awaveform is used for the recording and reproducing area 40.

[0162] Further, a fundamental waveform of a wobbling groove is oncondition of a sinusoidal waveform. However, the present invention isnot limited to the sinusoidal waveform. It is apparent that a cosinewaveform also exhibits the same effect.

[0163] A method of directly recording a data itself on an informationrecording medium 1 is explained above as a recording method for theinformation recording medium 1. However, a recording method according tothe present invention is not limited to the direct recording method. Ina case of recording a long data array by the direct recording method,there is existed a possibility that a plurality of “0s” or “1s” maycontinue and resulted in generating a DC component in the data array. Inorder to eliminate such a possibility, it is acceptable that the data ispreviously modulated by the base-band modulation method and recorded. Inother words, the method is that the data “0” and “1” are replaced withanother codes previously so as to reduce a sequence of “0”s and “1”s toa certain number or less. With respect to such a method, the method suchas Manchester code, PE (phase encoding) modulation, MFM (modifiedfrequency modulation), M2 (Miller squared) modulation, NRZI (non returnto zero inverted) modulation, NRZ (non return to zero) modulation, RZ(return to zero) modulation and differential modulation can be usedindependently or by combining some of them together.

[0164]FIG. 15 is a table exhibiting a change of fundamental data ofbefore and after a base-band modulation.

[0165] With respect to a base-band modulation method, which is mostsuitable for the information recording medium 1 of the presentinvention, it is the Manchester code (biphase modulation) method. TheManchester code method is a method of applying 2 bits to each one bit ofan original data to be recorded as shown in FIG. 15. That is, “00” or“11” is assigned to a data “0” to be recorded, and “01” or “10” to adata “1”. Further, an inverted code of inverting a last code ofpreceding data is essentially applied to a head code of succeeding datawhen arranging the succeeding data after the preceding data.

[0166]FIG. 16 is a table of definite example exhibiting a change of dataarray of before and after a base-band modulation. As shown in FIG. 16,an original data “100001” is assigned to be a code array of“010011001101”. The original data contains a sequence of four “0”s andis an asymmetrical data in which an appearing probability of “0” istwice that of “1”. If such an asymmetrical data is modulated by theManchester code method, a sequence of “0” or “1” is only two maximallyand the original data is converted into a symmetrical data having equalappearing probability of “0” and “1”. As mentioned above, the base-bandmodulation, which restricts a sequence of same bits within a certainquantity, is effective to increase stability of reading out a data.Consequently, the base-band modulation method is suitable forpre-treatment for a long array of location data.

[0167] With respect to a modulation method that is excellently suitableto the Manchester code method, there is existed the frequency-shiftkeying method as shown in FIG. 12. Particularly, in a case of afrequency-shift keying method in which phase difference of frequenciesbetween the high frequency section 501 and the low frequency section 500is assigned to be ±π/1.5, that is, 360—120 degrees, a frequency ratio ofhigh frequency to low frequency becomes 2.0, so that the frequency-shiftkeying method harmonizes with the Manchester code method that obtains a1-bit data from 2 bits and resulted in reducing an error when extractinga data.

[0168] Further, there is existed another method of highly analyzing alocation data and recording it in dispersion. For example, it is arecording method such that a location data is recorded as a combineddata array of “10X” in combination with a dummy data, wherein “X” iseither “0” or “1”, and the data array is allocated at everypredetermined interval. If the “X” is extracted by using the dummy data“10” as a data trigger, the original location data can be restored. Thismethod is effective for a format, which is allowed to read in a dataarray to be treated with taking a long period of time.

[0169] Furthermore, in a case that a changing-over point of a frequencyor a phase corresponds to a changing-over point of a data such as thefrequency-shift keying method and the phase-shift keying method, it isdesirable from a viewpoint of data that the changing is clearlyrecognized. From such a pint of view, there is existed a method thatmodulates a data previously by the differential modulation method.Actually, by converting an original signal modulated by the NRZImodulation method, for example, to another signal modulated by the RZmodulation method, a differential waveform of the NRZI signal can beproduced. A delayed waveform is produced first with respect to anoriginal waveform by the NRZI modulation, and then a bipolar waveform isproduced by differentiating between the original waveform and thedelayed waveform. By flipping over or folding back one polarity of thebipolar waveform to the other polarity, a RZ modulation waveform isgenerated.

[0170] [Second Embodiment]

[0171] The information recording mediums 1 and 2 in disciform areexemplified above. However, a shape of an information recording mediumaccording to the present invention is not limited to a disc shape. Anyshape such as a card can be applicable to the information recordingmedium of the present invention.

[0172]FIG. 17 is an information recording medium in a card shapeaccording to a second embodiment of the present invention. FIG. 18 isanother information recording medium in a card shape according to thesecond embodiment of the present invention. In FIG. 17, a card-shapedinformation recording medium 3 is composed of a read only area 33 formedin a strip and a recording and reproducing area 43 formed in a strip. InFIG. 18, another card-shaped information recording medium 4 is composedof a read only area 34 formed in a ring shape and a recording andreproducing area 44 formed in a ring shape.

[0173] [Third Embodiment]

[0174] A stacked information recording medium having multi-layers (notshown) can be constituted as a third embodiment of the present inventionby expanding the configuration of the information recording medium 1 ofthe present invention. For example, by laminating a substrate 13, afirst recording layer, a first light transmitting layer, a secondrecording layer and a second light transmitting layer in order, that is,by laminating a second recording layer and a second light transmittinglayer in order on a light transmitting layer 11 of the informationrecording medium 1, a stacked information recording medium having twolayers of recording layer can be realized. By this configuration,individual user data can be recorded in the first and second recordinglayers independently, and resulted in increasing a recording capacitytwice the recording capacity of the information recording medium 1.

[0175] Further, by laminating one set of the recording layer 12 and thelight transmitting layer 11 repeatedly, a stacked information recordingmedium having a plurality of recording layers such as triple andquadruple layers can be realized.

[0176] The information recording mediums 1 through 4 are explained indetails hereinbefore and fundamental areas of the present invention areexplained. However, it is apparent that many changes, modifications andvariations in the arrangement of equipment and devices and in materialswithout departing from the invention concept disclosed herein. Forexample, in the case of the information recording mediums 1 and 2 indisciform, its dimensions are not limited to one specific figure. Anydiameter within a range of 20 mm to 400 mm can be applied for theinformation recording mediums 1 and 2 in disciform. A diameter such as32, 41, 51, 60, 65, 80, 88, 120, 130, 200, 300 and 356 mm can beacceptable to the information recording mediums 1 and 2 in disciform.

[0177] Further, a wavelength of laser beam used for reproducing orrecording and reproducing information is defined to be 405 nm. However,the wavelength is not limited to 405 nm. Any wavelength such as 1300,980, 830, 780, 650, 635, 515, 460, 442, 430, 413 and 370 nm, and awavelength in the region of any of them can be used for a laser beam forreproducing or recording and reproducing information.

[0178] Furthermore, a numerical aperture NA of a lens is not limited to0.85. Any NA other than 0.85 such as 0.4, 0.45, 0.55, 0.60, 0.65, 0.7,0.75, 0.8 and 0.9 can be applicable to a lens. A lens having an NA ofmore than 1, which is represented by the solid immersion lens, can alsobe acceptable.

[0179] A reproduction power information, that is, a most suitablereproduction power for reproducing a recording and reproducing area 40can be previously recorded as one of control data in a read only area 30of an information recording medium 1 according to the present invention.The reproduction power information is most effective for a phase-changetype information recording medium 1 of which recording layer 12 isconstituted by a phase-change material. Such a phase-change material hasa merit of enabling to record a high-density record mark M easily by ahigh-power laser beam. On the contrary, the phase-change material isdefective in that a record mark M once recorded is easy to be erased bycontinuous irradiation of a laser beam in relatively lower power whilereproducing. In other words, so-called deterioration by reproductionlight is recognized. Consequently, selecting a laser power as low as arecord mark M is not erased actually is suitable for a reproducingapparatus. However, if the laser power is low, there is existed a defectthat a laser noise increases relatively. Particularly, in a case of aviolaceous laser beam that is emitted by a gallium nitride systemsemiconductor element as a light source, the deterioration byreproduction light appears remarkably. Therefore, in the phase-changerecording process by using a violaceous laser beam, flexibility ofselecting a reproduction power is extremely restricted and resulted inthat excellently reproducing a plurality of information recordingmediums 1, which are manufactured by a plurality of manufacturersindependently, becomes harder by a single reproduction power. However,if an information about an optimum reproduction power is recorded in apredetermined area of an information recording medium 1, wherein thepredetermined area is a read only area 30, a reproducing apparatus makesaccess to the read only area 30 first and collects an optimum value ofreproduction power, and then the reproducing apparatus can reproduceappropriately by feed-backing the optimum value to a power driver for areproduction laser beam. The collected optimum value of reproductionpower can be recorded in a memory device in the reproducing apparatusfor a while. Renewing an information about an optimum reproduction powerby resetting a previous information at each time when loading orreproducing an information recording medium 1 can always conduct theoptimum reproduction.

[0180] With respect to a method of collecting the optimum value ofreproduction power, that is, a method of reading out a control data thatcontains a value of reproduction power from a read only area 30hereupon, the control data is recorded by a wobbling groove not by arecord mark M, so that the control data can be read out in a relativelywide power range without deterioration by reproduction light.Consequently, if a reproducing apparatus is designed to read a read onlyarea 30 by a fixed laser power and to read a recording and reproducingarea 40 by a variable optimum laser power, an information recordingmedium 1 according to the present invention can be reproducedappropriately.

[0181] More accurately, the read only area 30 is read by a fixedrelatively higher laser power and the reproduction power is revised inaccordance with a collected data of optimum reproduction power, and thenthe recording and reproducing area 40 is reproduced by the revisedreproduction power.

[0182] In addition thereto, the reproduction power is changed whentraversing two areas. A push-pull signal is a differential signal in theradial direction, so that change of luminous energy of the reproductionpower when traversing two areas is relatively small and an impact whentraversing is very little.

[0183] As mentioned above, the reproducing apparatus and the reproducingmethod results in drawing a performance of the information recordingmediums 1 though 4 maximally.

[0184] Accordingly, an information recording medium of the presentinvention can be reproduced by an optimum condition, and resulted inthat a most suitable recording and reproducing system can beestablished.

[0185] As detailed above, according to an aspect of the presentinvention, there is provided an information recording medium 1, which iscomposed of at lease a read only area 30 and a recording and reproducingarea 40. By assigning each push-pull signal output of the read only area30 and the recording and reproducing area 40 to be within apredetermined range, a traversing reproduction across two areas can beconducted smoothly.

[0186] It should be understood that many modifications and adaptationsof the invention will become apparent to those skilled in the art and itis intended to encompass such obvious modifications and changes in thescope of the claims appended hereto.

What is claimed is:
 1. An information recording medium having at least aread only area and a recording and reproducing area comprising at least:a substrate; a recording layer formed on the substrate so as to recordand reproduce information; and a light transmission layer havingtransparency formed on the recording layer, the information recordingmedium is further characterized in that a wobbling groove correspondingto the read only area and another wobbling groove corresponding to therecording and reproducing area is formed on the substrate withoutoverlapping with each other, the recording and light transmitting layersare continuously adhered over at least two areas of the read only areaand the recording and reproducing area, reflectivity of the recordinglayer is more than 5%, and a push-pull signal output T3 reproduced fromthe read only area and another push-pull signal output T4 reproducedfrom the recording and reproducing area before recording satisfiesrelations of T3≧0.1, T4≧0.1 and 1.5≧T3/T4≧0.5.
 2. The informationrecording medium in accordance with claim 1, wherein the wobbling groovecorresponding to the read only area and the other wobbling groovecorresponding to the recording and reproducing area is recorded with adata in a wobbling shape by the any one modulation method of thefrequency-shift keying, phase-shift keying and the amplitude-shiftkeying methods.
 3. The information recording medium in accordance withclaim 2, wherein a phase difference between two frequencies is definedto be within a range of 360±15 degrees to 360±240 degrees when themodulation method is the frequency-shift keying method.
 4. Theinformation recording medium in accordance with claim 3, wherein a phasedifference of the frequency-shift keying method is 360±72 degrees. 5.The information recording medium in accordance with claim 2, whereinphase of a waveform by the frequency-shift keying method is selected soas for the waveform to be continuous at a changing-over point offrequency.
 6. The information recording medium in accordance with claim2, wherein the phase difference is defined to be within a range of λ/8to π when the modulation method is the phase-shift keying method.
 7. Theinformation recording medium in accordance with claim 2, wherein thedata is previously modulated by a base-band modulation method so as torestrict the continuing of the same bit to less than a predeterminedvalue.
 8. The information recording medium in accordance with claim 7,wherein the base-band modulation method is the Manchester code method.9. The information recording medium in accordance with claim 8, whereinthe modulation method is the frequency-shift keying method and a phasedifference between two frequencies is defined to be 360±120 degrees. 10.The information recording medium in accordance with claim 1, wherein thewobbling groove corresponding to the read only area is recorded with acontrol data in a wobbling shape.
 11. The information recording mediumin accordance with claim 1, wherein the other wobbling groovecorresponding to the recording and reproducing area is recorded with atleast a location data in a wobbling shape.
 12. The information recordingmedium in accordance with claim 11, wherein the other wobbling groovecorresponding to the recording and reproducing area is recorded with alocation data, which is referred when a recording is initiated and whilerecording, and a clock constituted by a single frequency is recorded ina wobbling shape between the other wobbling groove, which is recordedwith the location data.
 13. The information recording medium inaccordance with claim 1, wherein the read only area is recorded with avalue of optimum reproduction power for the recording and reproducingarea.
 14. The information recording medium in accordance with claim 1,wherein the wobbling groove corresponding to the read only area and theother wobbling groove corresponding to the recording and reproducingarea is formed on a groove side respectively.
 15. The informationrecording medium in accordance with claim 1, wherein a track pitch ofthe wobbling groove corresponding to the read only area is P3, anothertrack pitch of the other wobbling groove corresponding to the recordingand reproducing are is P4, a wavelength of reproducing light beam is λand a numerical aperture of an objective lens for reproduction is NA,the information recording medium is further characterized in that theP3, P4, λ and NA satisfies relations of P3≦λ/NA, P4≦λ/NA and P3>P4. 16.The information recording medium in accordance with claim 1, wherein thelight transmitting layer has a thickness of 0.02 mm to 0.12 mm.